Yeah so if you lose an arm my Fargo rating goes down, even though you had two arms when I played you. That's fair. There are advantages and disadvantages to doing it both ways. Take the OP, for example. If his rating is eventually lowered because his skills have diminished, should the skill levels of those who have played him go up, down, or remain the same? Probably none should go up, but who's to say which should go down and which should remain the same? It's all a guess, and letting a computer decide only gets you a deterministic guess. It's still a guess, and it's based on some human's opinion. So in the end you get an approximation of an opinion which, while more consistent and predictable, is by its very definition less accurate. In some respects it's better, in others it's worse.